Was working fine and then would not turn on. I have unplugged it and then plugged back in and held start button for 5 sec. Tried option command P-R, option V. No response, no sound no light on caps lock on keyboard, nothing. Is there an internal battery that needs to be replaced. If so where? Also have a 19" same year same problem. We have the screen out and blew it all out. My son repairs cell phones, not afraid to take all apart if necessary.